Textile Structure
how cloth is put together
Generator

A hem in 6 folds

A hem in 6 folds
A hem in 6 foldsA draped specimen seen from above. The outer circle is the flat specimen, the inner one the pedestal, and the wavy curve is the hem — whose amplitude is fixed by requiring it to be exactly as long as the specimen's edge, since cloth does not stretch.pedestal6 foldshem length 94.25specimen edge 94.25amplitude 24.8% of the meanhem runs 7.9–13.1drape coefficient 22.7%shadow, less the pedestal, overspecimen, less the pedestalamplitude solved from the hem's length, not chosenmean radius 10.5

A draped specimen seen from above. The outer circle is the flat specimen, the inner one the pedestal, and the wavy curve is the hem — whose amplitude is fixed by requiring it to be exactly as long as the specimen's edge, since cloth does not stretch.

3 essays call drape-hem. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the weave its essay argues about.

Where it is called

Changing this generator changes every one of these figures.

The cantilever test. A strip of cloth pushed out over an edge until its tip has drooped to the stated angle. The overhang at that moment gives the bending length, and cubing it with the mass per unit area gives the flexural rigidity. Mechanics and drape

Bending stiffness and the drape coefficient

Two standard measurements try to say how a fabric hangs. One measures a length and cubes it; the other measures an area and, on the geometry, turns out to be answering a different question from the one it is asked.

 What the drape coefficient answers to. The drape coefficient against the number of folds, and against how far the hem has come in. Over the range a real specimen shows, the fold count barely moves it; the hem radius moves it across almost its whole range. Mechanics and drape

A drape coefficient is one number for a directional thing

A fabric bends more easily one way than the other — a factor of two is ordinary. The drape test reports a single percentage, and the quantity that carries the directionality is the fold count, which the coefficient is almost blind to.

 The number the drape test does not record. A 150 mm specimen over a 90 mm pedestal, for fabrics from limp to stiff. The curve is the fold count the buckling argument predicts — three quarters of a power of the specimen's radius over its own bending length — and it runs from 2 folds to 11. The number beside each mark is the drape coefficient the same specimen would report, which moves by a few points across the whole range. Mechanics and drape

The nodes a drape test throws away

A drape test lays a circular specimen over a pedestal, photographs the shadow and reports one number. The specimen also falls into a definite number of folds, which is a buckling mode set by the fabric's own bending length — and the standard method observes it, does not record it, and reports the number it is least sensitive to.

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